This is how the Leader of the Opposition put it: “We say it is time for a change, a change of direction. We find an echo in the hearts and minds of people. They put it slightly differently. They say, ‘We can’t go on as we are, we can’t go on like this’.” The party leader in question was Margaret Thatcher, speaking on the eve of the 1979 election.

Three decades later, David Cameron channelled her dissatisfaction, populism and impatience on billboards across the land bearing the slogan: “We can’t go on like this.” And so, yesterday, did Ed Miliband, with his conference speech refrain: “Britain can do better than this.”

In four successive annual addresses of increasing power, the Labour leader has established his credentials as an orator of passion and force, the best his party has had since Neil Kinnock — which, by the way, I mean as a compliment. He is also a formidable rhetorician of the judo school, turning his opponents’ attacks against them. Cameron’s fixation with the “global race”, Miliband declared repeatedly, is a “race to the bottom”, a con trick to make the rich richer and the poor poorer.

All of which was good crowd-pleasing stuff, the tonic that the party badly needed after a lousy summer and the literary acid of Damian McBride’s memoirs. Context is all, and this was the right speech for the context. But the context will fast change, and, as compelling as Miliband’s speech was, what he did not say was no less significant than its actual content.

First and most counter-intuitively: he should have taken a leaf out of McBride’s book. Gordon Brown’s former communications supremo said that one of the purposes of his memoir was to confront Labour’s past, atone for it, and ensure that the party does not make the same mistakes again.

What was conspicuously lacking from Miliband’s speech was any true sense of regret about Labour’s past errors, its part in Britain’s economic difficulties, its role in cultivating the electorate’s cynicism in general. Widely publicised rehab is essential to all narratives of political recovery, and the absolute precondition of the process is that the party admits it has a problem — or, at least, that it says as much. Even at his final conference speech as leader in 2006, Blair was speaking over the heads of his tribe gathered in Manchester and apologising to the public for its past atavisims.

The heart of the matter — one of the central facts in British politics today — is that Miliband positively likes those atavisms. Far from seeking to purge the Labour movement’s primal instincts, he wants to cultivate them. True, he is reforming the link with the unions. But one had only to see Len McCluskey, the secretary general of Unite, reacting to the party leader’s speech yesterday to realise that the rift between the two men is about power not ideology.

“Red Ed is back”: this snap judgment fizzed across Twitter yesterday afternoon as tweeters of all ideological complexions drew a similar conclusion. Did he ever go away? Yes, in June, when he and Ed Balls “recalibrated” the party’s position on austerity and welfare, accepting that cuts would continue into the next Parliament and that Labour would impose its own benefit cap. But Miliband’s language yesterday was a reminder that he is, in every sense, a son of the Left.

Though it was scarcely a slogan, the most important phrase in the speech was “reset the market”. Miliband expressed this three-word ambition as part of his promise to freeze gas and electricity prices “until the start of 2017”. At a time when, for a great many voters, the cost of living seems out of sync with the statistics and graphs alleging national economic recovery, this pledge is a good old-fashioned “retail offer” to the punters on the doorstep. Yet the level of government intervention such a promise implies — price controls — is dramatically unlike what we have grown used to during and since the Thatcher era.

There remains some confusion over what, precisely, Miliband meant when he told developers “either use the land or lose the land”, but he certainly appeared to be threatening those who declined to build housing with government confiscation of their holdings. The land-grabbing state and the property-owning democracy: rarely do they coexist happily. But this was an unashamedly statist speech. I counted 36 uses of the word “government”.

At a Q & A this week, Miliband was asked: “When will you bring back socialism?” The Labour leader replied: “That’s what we are doing, sir.” This is a sincere project, too. The Labour leader is not a lazy tribalist who is clinging to old habits because he can’t be bothered to change. He genuinely believes that the financial crash and the social pathologies of the 21st century require a political response in which government plays a stronger part.

In his recoil from New Labour, he renounces not only the spin of McBride but the party’s embrace of the market, its military adventures, its nervous hugging of the centre. Like all true Marxist and post-Marxist thinkers, Miliband believes history has a direction and that Labour under his leadership should follow that Leftward trajectory. I don’t agree with him. But he acts from decent motives and is commendably forthright. The reds aren’t under the bed. They’re on the telly.

All of which leaves Cameron and Nick Clegg to slug it out for ownership of the boring old centre ground, the terrain that every party hates to occupy because it requires discipline, compromise and the taming of political zeal. Occupying the centre ground is exhausting: but in most circumstances, it also delivers the keys to No 10. Let’s see if Cameron, at his own party conference, has the energy, stamina and skills of captaincy to keep the Tories on the patch that Miliband has vacated once and for all. Onward to Manchester.

Matthew d’Ancona’s In It Together: The Inside Story of the Coalition Government (Viking) is published next week.